1. Field of the Invention
The present invention relates to the field of semiconductor manufacturing. Specifically, the invention relates to improved methods for curing semiconductor thin films, and more specifically, the invention relates to methods for regulating the temperature and temperature changes to which semiconductor thin films are exposed during the curing process. The invention also relates to semiconductor products made using the curing processes.
2. Discussion of the Related Art
Interlayer dielectric layers comprise insulating materials whose purpose is to electrically separate conductive elements of integrated circuits. One property of dielectric materials is the dielectric constant. For certain purposes it is desirable to use materials with low dielectric constants. The manufacture of interlayer dielectric semiconductor thin films is typically carried out by first depositing the desired thin film on a semiconductor substrate. One common way of depositing thin films is by spin-on deposition. During spin-on deposition, a solution of precursor for the thin film is applied to a semiconductor wafer, and thereafter, the wafer is rotated at sufficiently high speed (rapid spinning step) to thin and even the layer of precursor solution. After the rapid spinning step, the solvents are permitted to evaporate, leaving a dried film of dielectric material. However, typically, some of the commonly used dielectric materials require subsequent processing, including curing the thin film at high temperature. The high temperature curing step can cross-link the precursor molecules together, making a tighter, stronger film with a low dielectric constant.
Unfortunately, the currently available methods for curing spin-on deposition films are inadequate for producing high-quality thin films. In one example of a prior art method, after a precursor solution is allowed to dry on a semiconductor wafer, the wafer is typically placed in a pre-heated oven or furnace to cure the thin film. SiO.sub.2 --like films are typically cured at a temperature of about 400.degree. C. The wafer is maintained at that high temperature for about one hour, and is then removed from the curing oven. Such treatments have disadvantages. If the wafer is placed into an oven pre-heated to a temperature that is too high, the thin film is subjected to high thermal/mechanical stress, and can crack, becoming weak and having an undesirably low dielectric strength and mechanical strength. Similarly, if the wafer is abruptly removed from the heated oven, the rate of cooling can be too high, causing high thermal/mechanical stresses, which degrade the performance of the film. Moreover, in the manufacture of multilayered films, with several levels of semiconductor features, the repeated heating and cooling of the underlying layers can cause progressively greater defects in the films.
Therefore, methods are needed which result in the rapid, efficient curing of spin-on thin films, while maintaining the desired low dielectric constant, high dielectric efficiency, and high mechanical strength.